The Louisiana Democrat. [volume] (Alexandria, La.) 1845-1918, 1887-06-15
CHEMISTRY OF SOAP.

Interesting Information Regarding Hs
Composition and Effects.
That important article OF household
use. soap is of considerable interest
from chemical point of view. 1t is
true salt, or compound OF an acid and
in which the acids occurring in fats,
where they are combined with glycer-
inc as a base, are separated from it, and
combined with the alkali soda or pot
ash. Soaps in which the fatty acids
arc combined with lime. magnesla, lead
or iron are also known, but are only
used for medical purposes. The crys-
talline salts of soda are, as general
rule, efflorescent; that is, on exposure
to the air they give off moisture, and
crumble into dry powder.
Potash salts. on the other
hand, are oftener delinquescent,
absorbing moisture from the air, and
becoming liquid. This is also true OF
the soaps made from these alkalies;
hard soap being made from soda. and
soft soap from potash. A good soap
should be perfectly neutral. containing
neither excess of fatty acids or alkall.
An excess of free alkali in soap will
increase its cleansing power, but has
an injurious effect upon the skin and
clothing. 1t is common practice to
add carbonate of soda to laundry soap
for a similar purpose, but its can not
be recommended. The cleansing &C.
ton of the soap can not be very salts.
factorily explained, but it is doubtless
due to the alkali contained in it.
Probably some sort of double decom-
position takes place between the soap
and the greasy impurities OF the
skin or soiled linen, by which they
are rendered soluble in water. Wash
inc powders are almost always COM
posed of carbonate of soda. They may
occasionally be of use in removing
very obstinate spots, but their constant
use causes the clothing to wear out
very rapidly. Borax is less objection
able, and may sometimes serve good
purpose as an auxiliary to the soap.
Ammonia will often remove stains
which are not affected by the ordinary
cleansing process, but so powerful an
agent should be used with care. The
process of bluing illustrates an impor-
tant law of color. Freshly washed
linen is of slightly yellowsh tint.
which appears to be an optical illusion
dependingupon its excessive whiteness.
Now, blue and yellow are complement
ary colors; that is, when blue and
yellow light are combined, white
light is formed. So the addition OF a
trace of blue color to the linen neu-
tralizes the yellow tint, and renders it
apparently perfectly white. Bluing
is usually made from indigo, though
Prussian blue, ultramarine and aniline
blue are sometimes used. The same
process of bluing is applied to sugar
to give it whittier appearance. Starch
is vegetable product, usually pro.
cured from potatoes, and. when in
its natural state, consists of separate
grains easily distinguished under the
microscope. Upon boiling with wa,
ter, these grains burst open, and the
contents are partially dissolved in
the water. Upon cooling, it forms q
viscid jelly, or rather emulsion. as the
starch seems to be more in q state o.
minute subdivision than in Z
condition of solution When cloth
is saturated with it, ant
pressed with hot iron, the starch is
transformed into gummy substance.
which gives the requisite stiffness tc
the linen. The polished appearance
which is sometimes given to starchet
articles is produced by adding various
substances to the starch, among which
are gum aratic, gelatine or paraffine
OF the most important article used il
the laundry, water, there is little to b.
said We may mention, however, tina
the object of sprinkling dry clothin
before ironing is that the stear
formed by the heat of the iron ma
soften the cloth, and allow it to b
pressed smooth, 1t is also to be note
that clothing will dry in the air whel
the temperature is below freezing a
well as on warmer days, thus showing
that water cvaporates, even when in
frozen condition. -- Popular Scisnc
NetUS.